Commas are designed to help writers avoid confusing sentences and to clarify the logic of their sentences.
If you cook Jeff will clean the dishes. (Will you cook Jeff?)
While we were eating a rattlesnake approached us. (Were we eating a rattlesnake?)
Comma Rule 1: Use a comma before a coordinating conjunction (FANBOYS) joining two independent clauses.
Rattlesnakes are high in protein, but I’d rather eat a peanut butter sandwich.
Rattlesnakes are dangerous, and the desert species are even more so.
We are a proud people, for our ancestors passed down these famous delicacies over a period of five thousand years.
The exception to rule 1 is when the two independent clauses are short:
The plane took off and we were on our way.
Comma Rule 2: Use a comma after an introductory clause or phrase.
When Jeff Henderson was in prison, he developed an appetite for reading.
In the nearby room, the TV is blaring full blast.
Tanning in the hot Hermosa Beach sun for over two hours, I realized I had better call it a day.
The exception is when the short adverb clause or phrase is short and doesn’t create the possibility of a misreading:
In no time we were at 2,800 feet.
Comma Rule 3: Use a comma between all items in a series.
Jeff Henderson found redemption through hard work, self-reinvention, and social altruism.
Finding his passion, mastering his craft, and giving back to the community were all part of Jeff Henderson’s self-reinvention.
Comma Rule 4: Use a comma between coordinate adjectives not joined with “and.” Do not use a comma between cumulative adjectives.
The adjectives below are called coordinate because they modify the noun separately:
Jeff Henderson is a passionate, articulate, wise speaker.
The adjectives above are coordinate because they can be joined with “and.” Jeff Henderson is passionate and articulate and wise.
Adjectives that do not modify the noun separately are cumulative.
Three large gray shapes moved slowly toward us.
Chocolate fudge peanut butter swirl coconut cake is divine.
Comma Rule 5: Use commas to set off nonrestrictive (nonessential) elements.
Restrictive or essential information doesn’t have a comma:
For school the students need notebooks that are college-ruled.
Jeff’s cat that just had kittens became very aggressive.
Nonrestrictive:
For school the students need college-ruled notebooks, which are on sale at the bookstore.
Jeff Henderson’s mansion, which is located in Las Vegas, has a state-of-the-art kitchen.
My youngest sister, who plays left wing on the soccer team, now lives at The Sands, a beach house near Los Angeles.
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